One application where a plurality of frangible posts is used is in the construction of a guardrail or barrier systems for roading networks. The present invention will now for ease of reference only be described in relation to use in roading networks and barrier systems. However, it will be appreciated that there are a number of different applications where frangible post(s) may be required.
In the construction of roadside barriers, it is desirable on one hand to have a post that can provide sufficient support to withstand a typical side-on impact between an errant vehicle and the barrier. For example, where an impact of an errant vehicle occurs in a direction substantially laterally with respect to the direction of the post or road, the post provides the barrier with the ability to redirect the vehicle. However on the other hand, it is also desirable that the same post should be sufficiently weakened so as to yield during end-on impacts between an errant vehicle and the barrier, to thereby in most cases reduce the severity of impact forces experienced by the occupants of the vehicle.
There are number of methods currently known to produce frangible posts having a region of weakness making them suitable for use in roadside barriers. One such typical conventional method usually involves cutting out a portion of the post to form a series of holes, slots or notches either on the side of or within the post member. Such a method is described in U.S. Pat. No. 6,793,204, where elongated slots are formed within the post members. However one drawback with this method is that it produces an unnecessary waste of post material, which is needlessly expensive.
Another typical method for producing a region of weakness in a post is described in U.S. Pat. No. 6,398,192. In this patent, the post is cut into two segments, which are then rejoined by bolting or plug welding so as to create a region of weakness at the join.
One disadvantage with these current methods is that they require a number of steps, and/or the steps all involve a degree of skill and technique in order to form a suitable weakened region. This is particularly important for methods where the posts are cut and subsequently rejoined together. Another disadvantage with the current methods is that the weakened region has to be created prior to the post being used in the construction of the barrier. This unnecessarily increases the costs and time in manufacturing the post and/or barrier, as further materials and labor is required to be expended.
It would therefore be useful if there could be provided a method of producing a region of weakness in a post which is straightforward and easy to implement. Furthermore, a method which ensures the region of weakness is always located in the correct position on a post along with being in the correct orientation with respect to the road would be advantageous. It would also be a great benefit if there could be provided a method which could be undertaken on a site and/or undertaken even after a post has been used in the construction of a barrier.
It is an object of the present invention to address one or more of the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.